This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. We use X-ray crystallography, combined with other biophysical and biochemical methods, to study the structure and function of the Eph receptors and their interactions with the ephrin ligands. We also study the interactions of Ephs and ephrins with other binding partners, including the Henipavirus cell-attachment proteins.